Castle Markree in County Sligo is the ancestral home of the Cooper family. It was first acquired in 1663 by Edward Cooper from Oliver Cromwell, as compensation for Cooper's help in defeating the O’Brien clan. It has been in the Cooper family’s possession ever since, except for a brief occupation by the Catholic army during the Williamite War and during the Irish Civil War, when it was used by the Irish Free State Army.

The castle’s design was updated in 1802 and again in 1896, by architect Francis Johnson, who was also behind a number of Dublin landmarks including the GPO and the Bank of Ireland building on College Green. After sitting derelict for a number of years it was purchased from another family member in 1989 by Charles and Mary Cooper, the 10th generation of the Cooper family to live there. They transformed the castle into a hotel, which has hosted a number of famous guests including Johnny Cash.

The castle sits on 243 acres of land and includes a private observatory that holds the record for the lowest air temperature ever recorded in Ireland: -2.4 degrees Fahrenheit on January 16, 1881.

While the price for the castle is only available on the application, it is believed the going rate is approximately $3.6m, the same price as many considerably less palatial apartments in New York City, London and even Dublin.